Where 4.7 GB was until recently the maximum storage capacity for rewritable optical discs, phase-change DVD-RAM media with a storage capacity of tens of gigabytes are now available. DVD-RAM media are already used as a storage medium in the computer industry, and are expected to soon be used as a recording and playback medium in the audio-video (AV) field as a result of the development of economical encoders and decoders implementing the MPEG-1 and MPEG-2 digital AV data coding standards.
Digital broadcasting has already started in Japan, making it possible to multiplex video, audio, and data for multiple programs to an MPEG transport stream (MPEG-TS below). Digital broadcast recorders using hard disk drives or DVD drives are also available.
These next-generation digital broadcast recorders often record the broadcast content as it was broadcast without converting the MPEG-TS. So that the recorder does not need to be able to internally process both the MPEG-TS and MPEG program stream (MPEG-PS below), these recorders are expected to encode even external analog AV content from line input terminals (i.e., user content) to the MPEG-TS for recording.
The current DVD theoretical standards (such as DVD-Video, DVD-Audio, DVD Video Recording, and DVD Stream Recording standards) use the MPEG-PS for AV stream recording. This means that to convert content recorded using the MPEG-TS, such as in the above digital broadcast recorder, to the DVD-Video format, for example, the MPEG-TS must be converted to an MPEG-PS.
Converting an MPEG-TS multiplexed content stream to an MPEG-PS, however, requires complex computations for decoder buffer management. The conversion process therefore takes longer, requires re-encoding the elementary stream, may degrade the image and sound quality, and is thus generally difficult to accomplish.